An endless track belt assembly for propelling a snowmobile over snow, ice, or other similar ground structure typically, as illustrated for example in FIG. 1, comprises an endless elongated body 100 going around a rear wheel 220 and a front wheel 180, and having a ground-engaging outer surface and an inner surface. The track belt assembly receives and supports, on a lower run thereof, a suspension comprising a plurality of guide wheels 240, and guide rails 260. The ground-engaging surface typically bears a series of spaced traction lugs 160.
In FIG. 2(A), small guiding wheels 10 are positioned transversally in aligned pairs along guide rails 12 of the track, shocks being provided between the guide rails 12.
It is known that the noise generated by tracked vehicle such as snowmobiles is essentially produced by the endless belt track thereof. An analysis of a frequency spectrum of the noise generated by a tracked vehicle shows a main peak at a frequency corresponding to a driving frequency of the track belt and to harmonics thereof.
The driving frequency Fe of the track belt may be calculated from a number n of tooth of the wheel and a speed of rotation rpm of the wheel in turn per minute, using the following relation:
            F      e        =                  n        ·        rpm            60        ⁢        
Since the track has a constant pitch, factors that may modify the driving frequency thereof may comprise the mounting of the wheel, an action of the guiding wheels on the reinforcing rods, an action of the small guiding wheels on the guide rails, an action of the traction clips on the guide rails and an impact of the profiles with the ground, for example.
One of several methods actually contemplated for reducing an occurrence of peaks in acoustic spectra of tracked vehicle associated with repetitive events consists of breaking such repetitive sequences by causing a random spreading of the different events submitted to the track. The result is a distribution of energy on different harmonics of the critical frequency Fe.
It has been suggested to create such a random spreading by providing non-regular profiles on the ground-engaging surface of the track for example.
It has also been suggested to provide clips on each profile of the track.
There is still a need in the art for endless track belts producing reduced noise.